Lanthanide
Triangles Sandwiched by Tetranuclear Copper Complexes Afford a Family
of Hendecanuclear Heterometallic Complexes [Ln<sup>III</sup><sub>3</sub>Cu<sup>II</sup><sub>8</sub>] (Ln = La–Lu): Synthesis and Magnetostructural
Studies
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Abstract
Reaction
in ethanol of 3-hydroxymethylen-5-methylsalicylaldoxime (<b>H</b><sub><b>3</b></sub><b>L</b>) with CuCl<sub>2</sub>·2H<sub>2</sub>O and LnCl<sub>3</sub>·<i>x</i>H<sub>2</sub>O [Ln = La (<b>1</b>), Ce (<b>2</b>), Pr (<b>3</b>), Nd (<b>4</b>), Eu (<b>5</b>), Gd (<b>6</b>),
Tb (<b>7</b>), Dy (<b>8</b>), Er (<b>9</b>), Yb
(<b>10</b>), Lu (<b>11</b>), Ho (<b>12</b>)] allowed
the synthesis of a family of hendecanuclear heterometallic copper(II)–lanthanide(III)
clusters with general formula [Ln<sup>III</sup><sub>3</sub>Cu<sup>II</sup><sub>8</sub>(<b>HL</b>)<sub>6</sub>(μ<sub>4</sub>-O)<sub>2</sub>Cl<sub>6</sub>(H<sub>2</sub>O)<sub>8</sub>]Cl<sub>3</sub> (<b>1</b>–<b>12</b>). According to the
single-crystal X-ray diffraction investigation, the complexes are
isomorphous and crystallize in the trigonal <i>R</i>32 group.
The hendecanuclear cluster is formed by two tetrahedral μ<sub>4</sub>-oxo {Cu<sub>4</sub>} clusters assembled by three lanthanide
ions sandwiched in between. Along the family, the separation between
the {Cu<sub>4</sub>} moieties increases linearly from Lu to La in
good correlation with ionic radius of the lanthanide ions. A comparative
analysis of the magnetic data for the lanthanum (<b>1</b>) and
lutetium (<b>11</b>) compounds shows the presence of ferromagnetic
and antiferromagnetic interactions within the μ<sub>4</sub>-oxo
{Cu<sub>4</sub>} moieties. For the gadolinium (<b>6</b>) and
terbium (<b>7</b>) compounds, the magnetic interactions between
the lanthanide and the copper ions are found to be ferromagnetic.
The dysprosium (<b>8</b>) compound exhibits single-molecule
magnet behavior